JPS63267905A - Production of optical fiber cable - Google Patents

Abstract

PURPOSE:To suppress the reduction in the breaking life and the increase in the loss of light to obtain a required excess length with a high precision by arranging an intermediate winder, which has a drum whose diameter is smaller than that of a take-up drum, between a cooling device and a take-up device. CONSTITUTION:An intermediate winder 19 which has a winding drum 20 around which an optical fiber cable 10 should be wound is arranged following a tractive device 12. The outside diameter of this winding drum 20 is smaller than that of a take-up drum 15 (the body diameter of the take-up drum) arranged in a take-up device 14 which takes up the optical fiber cable 10 finally. If the optical fiber cable 10 is wound in one layer when being wound around the winding drum 20 of the intermediate winder 19, a certain excess length rate is secured. Thus, an excess length of the optical fiber is given with a high precision, and the reliability of the breaking life or the like is secured.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing an optical fiber cable in which an optical fiber strand or core is accommodated with extra length. The intermediate winding installed in front of the winding device is done after giving the required extra length to the optical fiber or core wire in advance.
The present invention relates to a manufacturing method for winding a cable using a cable winding device.

(Prior Art) FIG. 5 is an explanatory diagram of a typical conventional optical fiber cable manufacturing method, in which 1 indicates an optical fiber bare wire or core wire (
or an optical fiber unit 2) that is a collection of optical fibers or cores, 3 is a feeding device for the optical fibers or cores (or an optical fiber unit 2 that is a collection of optical fibers or cores), and 4 is a tensile strength 5 is a tensile strength body feeding device, 6 is a collecting die, 7 is a cable core, 8 is a plastic extruder, 9 is a crosshead of the extruder 8, 10 is an optical fiber cable, 11 is a cooling device, 12
13 and 13' are a traction device, 13 and 13' are traction caterpillars, 14 is a winding device, and 15 is a winding drum.

In FIG. 5, an optical fiber strand or core 1 (or an optical fiber unit 2 in which optical fibers or cores are collected) is fed out from a feeding device 3, and a tensile strength body 4 is fed out from a tensile strength body feeding device 5, and then assembled. Collected on dice 6. The assembled cable cores 7 are passed through an extruder 8
The optical fiber cable 10 is coated by extruding plastic onto the outer periphery of the cable core 7 in the crosshead 9 of the extruder 8.

The optical fiber cable 10 passes through a cooling device 11 such as a water tank, and at this time, the plastic extruded and coated onto the cable core 7 is cooled and solidified. optical fiber cable 10
is pulled between the traction caterpillars 13 and 13' of the traction device 12, sent to the winding device 14, and wound onto the winding drum 15. In this case, the feeding portions of the optical fiber or core 1 (or the optical fiber unit 2 in which the optical fiber or core is assembled), the tensile strength member 4, etc. rotate around the central axis of the cable core 7, and the cable Sometimes a twist is added to the core 7.

FIG. 1 is a sectional view of an optical fiber cable manufactured by the optical fiber cable manufacturing method of the present invention, in which numeral 16 is a cable jacket and 17 is a pipe-shaped space. This cable is an optical fiber or core 1 (or an optical fiber unit 2 that is a collection of optical fibers or cores)
The tensile strength member 4.4 is placed eccentrically from the center of the cable.
The cable is loosely accommodated in a pipe-shaped space 17 formed by a cable jacket 16 including the cable sheath 16. Both the pipe-shaped space 17 and the tensile strength member 4.4' are formed without twisting the center of the cable, and do not include a twisting process, which simplifies the manufacturing equipment and manufacturing process, and speeds up the manufacturing process. It is possible to improve the In addition, by utilizing the fact that the neutral plane of cable bending can be set arbitrarily depending on the positions of the pipe-shaped space 17 and the tensile strength member 4° 4', the pipe-shaped space 17 can be stretched to an appropriate degree when the cable is wound onto a drum during manufacturing. can be granted.

Therefore, by accommodating the optical fiber or the core wire 1 in the pipe-shaped space 17 in the stretched state, the pipe-shaped space 17 is not stretched to its original state during cable extension. , so the optical fiber within the cable has extra length. This extra length can be determined by the cable structure and the diameter of the winding drum, and it is possible to control the extra length of the optical fiber. Therefore, it is possible to suppress the optical fiber from being pulled in or protruded, distortion, etc. when the cable is stretched or bent.

In order to manufacture optical fiber cables with this structure,
Conventionally, a manufacturing method as shown in FIG. 5 has been used.

However, the extra length given to the optical fiber strand or core wire in the optical fiber cable depends on the diameter of the cable winding drum, and it is not possible to freely select the type of drum to be used. . Furthermore, in the case of cables of several tens of meters or more, the cables are wound around the drum in many layers, so the bending diameter of the cable changes from layer to layer, making it impossible to provide the required extra length with high accuracy. Furthermore, in conventional manufacturing methods, optical fiber strands or core wires 1
Since the coefficient of friction between the optical fiber unit 2 (or the optical fiber unit 2 which is a collection of optical fibers or cores) and the inner wall of the pipe-shaped space 17 is small, the optical fibers or cores 1
Pack tension applied to the optical fiber or core 1 (or the optical fiber unit 2 that is a collection of optical fibers or cores) when it is fed out (or the optical fiber unit 2 that is a collection of optical fibers or cores) (Tension applied to the optical fiber strand or core wire 1 in the direction of the feeding device 3) reaches the winding drum 15. Therefore, the optical fiber cable 10 is
When the optical fiber is wound into a pipe-like space, the optical fiber or core 1 (or the optical fiber unit 2, which is a collection of optical fibers or cores) has an elongation strain caused by the back tension. It is housed in section 17. The elongation strain caused in the optical fiber by this back tension is called residual strain. When a single core wire formed by applying a plastic coating to each optical fiber is accommodated in a cable, the residual strain is about 0.04% to 0.1%. Residual strain of this value may have a significant effect on the rupture life of the optical fiber, which is a brittle body, and may shorten the actual usage time of the optical fiber cable or cause a series of failures.

Furthermore, since tensile stress is generated in the optical fiber 18 (FIG. 2) due to residual strain, this tensile stress σ and the bending of the optical fiber 18 (because the optical fiber cable 10 is wound on the winding drum 15) ), the optical fiber 18
A force (lateral pressure) F=σ in the axial direction of the winding drum 15 as shown in FIG.
A/R (A: cross-sectional area of the optical fiber, R: optical fiber bending radius) occurs. This lateral pressure F causes a microbend (minor bend) in the optical fiber 18, resulting in an increase in optical loss. Furthermore, the surplus length ratio [((length of optical fiber bare wire or core wire 1, etc. accommodated in the cable) - (cable length)} ÷ (cable length)] β1 is set for the optical fiber bare wire or core wire 1, etc. Even if the cable structure (positions of tensile strength members 4, 4', etc.) is designed to give this, residual strain εr actually exists during manufacturing. , the optical fiber has residual strain ε after the cable is stretched.

Since it contracts by that amount and returns to its original length, the extra length β1 becomes a small value by the amount of residual strain εr, which has the drawback that it is not possible to ensure practically sufficient characteristics.

In this way, when providing extra length to the optical fiber housed within the cable due to the cable structure, if the optical fiber cable is manufactured using conventional manufacturing methods, the required extra length of the optical fiber housed within the cable can be precisely adjusted. Since it is difficult to apply the strain well and residual strain is generated in the optical fiber, there is a drawback that an optical fiber cable having the desired characteristics cannot be realized.

(Problems to be Solved by the Invention) The present invention solves the problem by removing the residual strain that occurs in the optical fiber when winding the cable in the production of an optical fiber cable that provides extra length to the optical fiber accommodated in the cable structure. It is an object of the present invention to provide a method for manufacturing an optical fiber cable, which suppresses the shortening of the breakage life of the optical fiber and the increase in optical loss, and allows the required extra length to be accurately given to the optical fiber within the cable.

(Means for Solving the Problems) In the optical fiber cable manufacturing method of the present invention, in the optical fiber cable manufacturing process, the outer diameter of the winding drum (the drum body) is diameter)
For winding a cable with a smaller outer diameter, a drum is arranged, and after the cable is wound around the drum, it is wound up by a winding device.

In conventional optical fiber cable manufacturing methods, the cable is not wound around a drum in front of an optical fiber cable winding device.

(Embodiment) FIG. 3 is a diagram showing an embodiment of the optical fiber cable manufacturing method of the present invention, in which 19 is a device for intermediate winding, and 20 is a drum for winding. A manufacturing method for manufacturing a cable having the structure shown in FIG. 1 will be described below.

The optical fiber strands or core wires 1 (or the optical fiber unit 2 in which the optical fiber strands or core wires 1 are assembled) and the tensile strength body are fed out from the feeding device 3 and the tensile strength body feeding device 5 while applying bank tension, respectively. 4 passes through the collecting die 6 and is placed correspondingly to the cable structure. The aggregate thus formed after passing through the collecting die 6 then passes through an extruder 8 that extrudes plastics such as polyethylene and polyvinyl chloride.

At this time, the pipe-shaped space 17 shown in FIG.
A cable jacket 16 having a diameter is extruded and formed.

The optical fiber cable 10 formed in this way is
In order to harden the cable jacket 16, which has softened at high temperatures, it passes through a cooling device 11 and is cooled. Generally, a water tank is used as the cooling device 11. The optical fiber cable 10 that has passed through the cooling device 11 is sandwiched between the traction caterpillars 13 and 13' of the traction device 12, and the traction caterpillars 1
3.13' rotation pulls it in the direction of the winding device 14. The manufacturing method up to this point has been conventional, and conventional manufacturing equipment can also be applied.

In the present invention, next to the traction device 12, the optical fiber cable 1
0 winding is characterized by the arrangement of the intermediate winding device 19 with the drum 20. Moreover, in this winding, the outer diameter of the drum 20 is the same as that of the winding drum 15 installed in the winding device 14 that finally winds the optical fiber cable 10.
(the diameter of the winding drum).

This winding will be explained below regarding determination of the diameter of the drum 20.

The optical fiber cable 10 shown in FIG. 1 has the bending rigidity of the cable in a specific bending direction (direction of arrow a in the figure) depending on the dimensions and positions in the cross section of the pipe-shaped space 17 and the tensile strength member 4.4'. The bending midplane m-n (plane where no elongation or compression strain occurs in the longitudinal direction of the cable when the cable is bent) can be minimized and the bending midplane m-n (plane where no elongation or compression strain occurs in the longitudinal direction of the cable when the cable is bent) can be made into an optical fiber strand or core wire. It can be set inside the bend of the cable than the first grade (Reference 1: M,
Kawase, et al., “A new opti
cal fiber cable design”, F
irst 0ptoelectronics Conf
erence(OEC'86) Technical
Digest, pp, 102-103.1986)
*Therefore, when a cable having such a structure is bent in the direction of arrow a, the pipe-like space 17 is elongated, and the elongation is approximately inversely proportional to the bending diameter. In the conventional manufacturing method shown in FIG.
5, the pipe-like space 17 is expanded. At this time, if the optical fiber strand or core wire 1 is fed into the pipe in a state where no stretching strain occurs and the bending diameter is constant, when the optical fiber cable 10 is stretched, there will be no damage inside the pipe. An optical fiber strand or core wire 1 or the like having an extra length corresponding to the extension of the pipe-shaped space 17 is accommodated.

In other words, the distance from the inside surface of the optical fiber cable 10 to the bending neutral plane m-n is do, and the bending neutral plane m-n is
If the distance from C1 to the position where the optical fiber strand or core wire 1, etc. is arranged is C1 and the bending diameter is 2r, the surplus length ratio β given to the optical fiber fiber or core wire 1, etc. is given by the following formula. .

β=C/ (r+dc) (1) However, in the actual manufacturing process, when a cable of tens of meters or more is wound around a drum, the cable is wound around the drum in many layers, so the bending diameter of the cable is The diameter of the drum body is set as the minimum, and the diameter increases gradually beyond that, and does not become constant.

Therefore, the extra length within the cable changes in the longitudinal direction of the cable. Further, since the extra length is determined by the cable structure and the same diameter of the drum, it is impossible to freely change the same diameter of the drum. Furthermore, in order to prevent slack from occurring in the optical fiber strand or core wire 1, etc.,
When unwinding, it is necessary to apply back tension while unwinding, and for this reason, an elongation strain εr is generated in the optical fiber strand or core wire 1, etc. due to the back tension. Therefore, in the conventional manufacturing method shown in FIG. The actual surplus length ratio β1 of the optical fiber strand or core wire 1 when the wire is extended is given by the following equation.

β force=β−εr (2) A case in which the optical fiber cable 10 is manufactured using the manufacturing method of the present invention shown in FIG. 3 will be described. Assuming that the diameter of the drum 20 is 2r, the intermediate winding of the device 19 is the position where the optical fiber cotton or core wire 1 is placed when the optical fiber cable 10 is wound around the drum 20. The elongation that occurs in the pipe-shaped space 17 at is expressed by the formula (
Corresponds to 1). β can be arbitrarily changed by adjusting the drum outer diameter 2r, and the optical fiber wire or core wire 1 having a surplus length ratio β can be drawn into the optical fiber cable 10 from the feeding device 3 side. Intermediate winding is done by device 19
When winding the optical fiber cable 10 around the drum 20, if the winding is -11 windings, r will be constant, and formula (1)
A constant surplus length ratio β can be secured from . That is, when the optical fiber cable 10 is wound around the winding drum 15, the optical fiber strand or core wire 1 having the surplus length ratio β is accommodated in the optical fiber cable 10, and the cable is wound in many layers on the winding drum 15. Also, a certain amount of extra length can always be added. In addition, in order to prevent residual strain εr from occurring in the optical fiber when the optical fiber cable 10 is wound around the winding drum 15, the intermediate winding is performed by the device E19, and an additional residual strain ε1 is added to the optical fiber cable 10 in advance. What is necessary is to draw in the optical fiber strand or core wire 1, etc. That is, for the intermediate winding, the diameter 2r of the drum 20 for the winding of the device 19 may be determined so as to satisfy equation (3).

β=β1+εr(3) When formula (1) is substituted into formula (3), the winding diameter 2r of the drum 20 is given by the following formula.

2r=2C/(β, +εr)−ac (4) In order to prevent stretching strain from occurring in the optical fiber housed in the optical fiber cable 10 wound around the winding drum 15, the diameter of the winding drum 15 must be 2R. From equation (1), it is necessary to satisfy the following equation.

β1≧C/(R+a,) (5) Therefore, the relationship between r and R in equations (1), (4), and (5) is as follows.

R≧(β·r+εr−d.)/(β−εr) (6) In other words, the diameter 2R of the winding drum 15 can be arbitrarily selected within a range that satisfies equation (6). By using the winding drum 20 and the winding drum 15 designed based on the formula (6), it is possible to accurately add extra length to the optical fiber strand or core wire 1 accommodated in the optical fiber cable 10. .

FIG. 4 shows another embodiment of the optical fiber cable manufacturing method of the present invention, in which the traction device 12 is removed from the embodiment shown in FIG. 3, and the intermediate winding applies traction force to the device 19. It doubles as a towing device.

(Effects of the Invention) According to the method for manufacturing an optical fiber cable of the present invention, the following effects can be obtained.

In manufacturing an optical fiber cable, the optical fiber is loosely accommodated in a pipe-shaped space, and the extra length of the accommodated optical fiber can be controlled by utilizing the elongation strain of the cable component when the cable is bent due to the cable structure. The extra length of the optical fiber can be provided with high precision.

This makes it possible to ensure reliability, such as the breakage life of the optical fiber during actual use of the cable. Further, it is possible to suppress residual strain in the drum-wound state immediately after the cable is manufactured, and it is possible to prevent breakage of the optical fiber and increase in optical loss. Furthermore, the outer diameter of the cable winding lid drum can be freely selected within a certain range.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an optical fiber cable manufactured by the optical fiber cable manufacturing method of the present invention, and Figure 2 shows the optical fiber cable in Figure 1 in a bent state, with the optical fiber in the cable having residual strain. Fig. 3 is an illustration of an embodiment of the optical fiber cable manufacturing method of the present invention, and Fig. 4 is an illustration of another embodiment of the optical fiber cable production method of the invention. , FIG. 5 is an explanatory diagram of a conventional method of manufacturing an optical fiber cable. 1... Optical fiber strand or core wire 2... Optical fiber unit 3... Feeding device 4.4'... Tensile strength member 5.
... Tensile strength body feeding device 6 ... Collection die 7 ... Cable core 8 ...
Extruder 9...Extruder cross head 10.
...Optical fiber cable 11...Cooling device 12...Traction device 13.1
3'... Traction caterpillar 14... Winding device 15... Winding drum 16
...Cable jacket 17...Pipe-shaped space 18.
...Optical fiber 19...Intermediate winding is done by device 20...
・Wrap on drum

Claims (1)

[Claims] 1. An optical fiber strand or core wire and a tensile strength body are supplied to an extruder crosshead, and a pipe-like shape having an inner dimension larger than the outer diameter of the optical fiber strand or core wire is provided on the outer periphery of the optical fiber strand or core wire. After the plastic is extruded and coated so that a space is formed and the tensile strength member is eccentrically arranged outside the pipe-shaped space, the plastic is cooled by a cooling device, and then the winding device is installed in a winding device. By winding the cable onto a drum, the neutral plane of the bend of the cable is set inside the cable bend from the accommodation position of the optical fiber element or core wire housed in the pipe-shaped space, and the optical fiber element is In the manufacturing process of forming an optical fiber cable in which extra length is added to the wire or core wire, an intermediate winding device having a drum having a smaller diameter than the winding drum is disposed between the cooling device and the winding device. While winding the optical fiber cable around the winding drum of the intermediate winding device, the optical fiber cable is passed through the intermediate winding device, and then wound around the winding drum of the winding device,
A method for manufacturing an optical fiber cable, comprising manufacturing an optical fiber cable. 2. Elongation strain that occurs in the optical fiber due to tension applied to the optical fiber strand or core wire supplied to the extruder crosshead, that is, {(elongation length of optical fiber due to tension) ÷ (optical fiber without tension) length)} is ε_r, and the distance from the inside surface of the bend of the optical fiber cable to the bending midplane is d
_c, the diameter of the winding drum of the intermediate winding device is 2R, the diameter of the winding drum is 2R, and when the optical fiber cable is wound around the winding drum, the cable is bent only by setting the neutral plane of cable bending. The surplus length ratio given to the optical fiber strand or core wire in the cable, that is, [{(length of the optical fiber strand or core wire housed in the cable) - (
Cable length)｝÷(cable length)] is β, and R≧(β
The method for manufacturing an optical fiber cable according to claim 1, wherein the following relationship is satisfied: -r+ε_r-d_c)÷(β-ε_r).